This paper describes an experimental investigation of whirl elimination of a hydrodynamic bearing with an electromagnetic exciter (EE) and includes a stability analysis through a root locus plot. The test apparatus incorporates the EE, which provides additional stiffness through a PD algorithm in order to stiffen a rotating machine to resolve fluid-induced instability. The stiffness of the hydrodynamic bearing gives a significant contribution to the occurrence of unstable vibrations as the speed or the load of a rotating machine increases. With regard to the whirl-eliminated investigations, the EE used to raise the stiffness of the rotating machine can cause important changes in the stability of the rotating machine. The threshold of stability derived in this paper that affects stability conditions can be used to define the stability margin of the rotating machine. A simple control scheme is used to calculate the amount of the supplemental stiffness supplied by the EE, and is confirmed through experiments. To offer a faster, more stable and more effective strategy for whirl elimination, the dynamic behavior of a rotor system affected by fluid-induced whirl instability phenomena has been successfully studied. (C) 2009 Elsevier Ltd. All rights reserved.
